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1
Content available Thermal behavior and kinetic decomposition of sweet potato starch by non-isothermal procedures
Liu Ying, Yang Liutao, Zhang Yingzhe
Archives of Thermodynamics
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2019
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Vol. 40, no 4
67--82
EN
In this study, X-ray diffraction, thermogravimetric analysis and differential scanning calorimetry (DSC) method were used to analyze the main characteristics of sweet potato starch, and to analyze the thermal degradation process of sweet potato starch. Specifically, X-ray diffraction to study its structure, thermogravimetric analysis to study the thermal degradation kinetics, and differential scanning calorimetry to study the thermogram of sweet potato starch. The thermal decomposition kinetics of sweet potato starch was examined within different heating rates in nitrogen atmosphere. Different models of kinetic analysis were used to calculate the activation energies using thermogravimetric data of the thermal degradation process. Activation energies obtained from Kissinger, Flynn-WallOzawa, and Šatava-Šesták models were 173.85, 174.87 and 174.34 kJ/mol, respectively. The values of activation energy indicated that the thermal degradation of the sweet potato starch was a single reaction mechanism or the combination of multi-reaction mechanisms. The differential scanning calorimetry analysis show that two decomposition stages were presented: the first at a low temperature involves the decomposition of long chain; and the second at a high temperature represents the scission of glucose ring. This information was helpful to design the processing process of many natural polymers. Thermogravimetric Fourier transform-infrared (TG–FTIR) analysis showed that the main pyrolysis products included water, methane, carbon dioxide, ammonia, and others.
2
Content available remote Kinetic analysis for biodesulfurization of dibenzothiophene using R. rhodochrous adsorbed on silica
Canales C., Eyzaguirre J., Baeza P., Aballay P., Ojeda J.
Ecological Chemistry and Engineering. S
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2018
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Vol. 25, nr 4
549--556
EN
Experimental biodesulfurization (BDS) data for dibenzothiophene (DBT) (1.0-7.0 mM) with Rhodococcus rhodochorus immobilized by adsorption on silica, were adjusted with liquid-film kinetic model (Fisher coefficient, F = 592.74 and probability value p << 0.05 and r 2 = 0.97). Simulations predict the presence of considerable amounts of DBT surrounding the particles, which would be available for the cells adsorbed on the surface of silica. The greatest percentage removal (50 %) was obtained for adsorbed cell system over the suspended bacterial cells (30 %), showing that sulfur substrates are more bioavailable when the bacterial cells are adsorbed on silica. The liquid-film modelling with diffusional effects provides proper theoretical basis to explain the BDS performance obtained using adsorbed cells.
3
Content available Reaction Kinetics and Morphological Study of TiNb2O7 Synthesized by Solid-State Reaction
Choi S. H., Ali B., Choi K. S., Hyun S. K., Sim J. J., Choi W. J., Joo W., Lim J. H., Lee T. H., Kim T. S., Park K. T.
Archives of Metallurgy and Materials
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2017
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Vol. 62, iss. 2B
1051--1056
EN
Although TiNb2O7 is regarded as a material with high application potential in lithium-ion batteries (LIBs) and solid-oxide fuel cells (SOFCs), it has been difficult to find suitable cost-effective conditions for synthesizing it on a commercial scale. In this study, TiNb2O7 compounds were synthesized by a solid state synthesis process. For stoichiometrically precise synthesis of the TiNb2O7 phase, the starting materials, TiO2 and Nb2O5 were taken in a 1:1 molar ratio. Activation energy and reaction kinetics of the system were investigated at various synthesis temperatures (800,1000,1200, and 1400°C) and for various holding durations (1,5,10, and 20 h). Furthermore, change in the product morphology and particle size distribution were also evaluated as a function of synthesis temperature and duration. Additionally, quantitative phase analysis was conducted using the Rietveld refinement method. It was found that increases in the synthesis temperature and holding time lead to increase in the mean particle size from 1 to 4.5 μm. The reaction rate constant for the synthesis reaction was also calculated.
4
Content available Thermal and kinetic analysis of pure and contaminated ionic liquid: 1-butyl-2.3-dimethylimidazolium chloride (BDMIMCl)
Muhammad A.
Polish Journal of Chemical Technology
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2016
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Vol. 18, nr 2
122--125
EN
In this research work, thermal decomposition and kinetic analysis of pure and contaminated imidazolium based ionic liquid (IL) has been investigated. As thermal decomposition and kinetics evaluation plays a pivotal role in effective process design. Therefore, thermal stability of pure 1-butyl-2,3-dimethylimidazolium chloride (BDMIMCl) was found to be higher than the sample of IL with the addition of 20% (wt.) NH4Cl as an impurity. The activation energy of thermal degradation of IL and other kinetic parameters were determined using Coats Redfern method. The activation energy for pure IL was reduced in the presence of NH4Cl as contaminant i.e., from 58.7 kJ/mol to 46.4 kJ/mol.
5
Content available Formation And Stabilization Of Silver Nanoparticles In Ethanol By Phosphinic Acid
Kim J.-K., Shim H.-M., Park M. J., Koo K.-K.
Archives of Metallurgy and Materials
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2015
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Vol. 60, iss. 2B
1293--1296
EN
Although phosphinic acid (H3PO2) has a powerful reduction potential, the reduction of silver ions by phosphinic acid salt has not yet been reported. In this work, colloidal silver has successfully synthesized by reducing silver ions in ethanol with phosphinic acid as a reducing agent. The effects of [AgNO3]/[H3PO2] ratios and reaction temperature were considered. Spherical silver nanoparticles with cubic structure were successfully prepared and their diameters were measured to be 8.5±0.9 nm − 11.3±0.2 nm. Half-life analysis showed that the reduction of silver ions proceeded with the reaction order of 1.30 on concentration of phosphinic acid and activation energy of 120.7 kJ/mol.
6
Content available remote Kinetic analysis of thermoluminescence glow curves in feldspar: evidence for a continuous distribution of energies
Pagonis V., Morthekai P., Kitis G.
Geochronometria
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2014
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Vol. 41, no. 2
168--177
EN
The thermoluminescence (TL) glow curves from feldspars have been the subject of numerous studies, because of their importance in luminescence dating and dosimetry. This paper presents new experimental TL glow curves in a plagioclase feldspar, measured using the T,sub>max–Tstop technique of glow curve analysis. Kinetic analysis of the experimental results is carried out for a freshly irradiated sample, as well as for a sample which has undergone optical treatment using infrared light for 100 s at 50°C. Application of the initial rise method of analysis indicates that the TL signals from both samples can be characterized by a continuous distribution of energy levels. By subtracting the TL glow curves measured at successive Tstop values, a series of TL glow curves is obtained which are analyzed using the empirical general order kinetics. It is found that all TL glow curves obtained by this subtractive procedure can be described accurately by the same general order parameter b ~1.7. In a second attempt to analyze the same TL glow curves and possibly extract information about the underlying luminescence process, the shape of TL glow curves is analyzed using a recently proposed physical kinetic model which describes localized electronic recombination in donor-acceptor pairs. Within this model, recombination is assumed to take place via the excited state of the donor, and nearest neighbor recombinations take place within a random distribution of centers. This recent model has been used recently to describe successfully several types of luminescence signals. This paper shows that it is possible to obtain good fits to the experimental data using either one of these two approaches.
7
Content available Kinetic Analysis of Aluminium Evaporation from the Ti-6Al-7Nb Alloy
Blacha L., Golak S., Jakovics A., Tucs A.
Archives of Metallurgy and Materials
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2014
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Vol. 59, iss. 1
275--279
EN
In the present paper, kinetics of aluminium evaporation from the Ti-6Al-7Nb alloy during smelting by means of the VIM method at 5 to 1000 Pa has been discussed. To determine the liquid titanium meniscus area and the liquid titanium mean velocity for the experimental conditions of the study, a methodology based on the coupled model of the electromagnetic field and the hydrodynamic field of liquid metal was applied.
PL
W prezentowanej pracy omówiono kinetykę procesu odparowania aluminium ze stopu Ti-6Al.-7Nb wytapianego metodą VIM w zakresie ciśnień od 5 do 1000Pa. Do wyznaczenia powierzchni| menisku ciekłego tytanu oraz średniej prędkości ciekłego tytanu wykorzystano model matematyczny procesu topienia i nagrzewania ciekłego metalu w piecu indukcyjnym uwzględniający sprzężenie pola elektromagnetycznego i pola hydrodynamicznego ciekłego metalu.
8
Content available Kinetic modeling of chromium(III) extraction with aliquat 336 from alkaline aqueous solutions containing chlorides
Wionczyk B.
Physicochemical Problems of Mineral Processing
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2013
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Vol. 49, iss. 2
587--605
EN
The effects of time, composition and history of preparation of the aqueous phase on the liquidliquid extraction of chromium(III) with Aliquat 336 from the aqueous alkaline solutions containing chlorides were studied. At time far from the equilibrium the yield and initial rate of the chromium(III) extraction depend on NaOH concentration, ionic strength of the aqueous phase and the way of its preparation. At the constant composition of the feed solution, rate of the Cr(III) extraction in approach to the equilibrium is higher when chromium(III) is extracted from the alkaline aqueous phase freshly prepared by direct dissolution of a weighted sample of CrCl3 than from that obtained by dilution of aged stock solution of CrCl3. Kinetic analysis by the mathematical models showed that within the whole period of time needed to reach the equilibrium, the rate of the Cr(III) extraction is limited by the second-, and third-order chemical reaction towards Cr(III), irrespective of composition and preparation history of the aqueous phase. The three-dimensional diffusion and chemical reaction at phase boundary substrateproduct (the contracting volume) models have a significant effect on the chromium(III) extraction within the initial extent of the process.
9
The Effects of Diluents on Sodium Ion Transport through Bulk Liquid Membrane with Crown Ether Carriers
Altin S., Peker I., Demircioglu N.
Polish Journal of Chemistry
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2009
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Vol. 83, nr 2
275-283
EN
In this study, the effects of the different mebrane diluents, carriers and variations in the concentrations of the carriers on the sodium ion transport were examined in bulk liquid mebrane systems. The kinetic analysis of the sodium ion transport in the liquid membrane was performed through the implementation of two consecutive kinetic equations of first order irreversible reactions and the relevant kinetic parameters (k1, k2a, k2m, Rmax, tmax) were determined. Toluene, n-hexane, 1-octanol, chloroform and dichloromethane were used as membrane diluents, while 18crown6 (18C6), dicyclohexyl 18crown6 (DC18C6) and dibenzo 18crown6 (DB18C6) were used as carriers. The results reveal that the best sodium ion transport was realized when toluene-dichloromethane (90%-10%) was used as the membrane, and 1×10-3 M DB18C6 was used as the carrier.
10
Content available remote Analiza kinetyczna usuwania zanieczyszczeń ze stali na drodze rafinacji próżniowej
Fornalczyk A., Oleksiak B.
Prace Instytutu Metalurgii Żelaza
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2006
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T. 58, nr 4
61-63
PL
Omówiono zjawisko parowania związków lotnych kąpieli metalowej (stali) w warunkach obniżonego ciśnienia, wraz z opisem kinetyki tego procesu. Przedstawiono możliwości oceny wartości współczynników przenikania masy w fazie ciekłej i gazowej.
EN
The effect of evaporation of volatile components of metal bath (steel) under the reduced pressure is discussed and kinetics of this process is described. The possibilities for evaluation of the values of mass transfer coefficients in the liquid and gaseous phase are presented.
11
Content available remote Analiza termodynamiczna i kinetyczna układu: ciekły nasycony węglem stop (Fe-C) - pary magnezu
Modrzyński A., Grześkowiak K.
Krzepnięcie Metali i Stopów
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2000
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R. 2, nr 44
239--248
PL
W artykule przeprowadzono analizę termodynamiczną reakcji zachodzących w układzie: ciekły nasycony węglem stop (Fe-C)-pary magnezu. Na podstawie przeprowadzonej analizy wykazano, że obróbka ciekłego żeliwa parami magnezu prowadzi do znacznego obniżenia aktywności tlenu i siarki w tym stopie. Proces wiązania tlenu i siarki prowadzi do wzrostu napięcia powierzchniowego na granicy: ciekłe żeliwo − zarodek grafitu poprzez obniżenie aktywności powierzchniowej tlenu i siarki. Nadmiar magnezu (przy małym stężeniu tlenu i siarki) może być przyczyną spadku wartości napięcia powierzchniowego wskutek dużej aktywności powierzchniowej tego pierwiastka. Przeprowadzono także analizę kinetyki w układzie: ciekły nasycony węglem stop (Fe-C) – pary magnezu. Podano równania opisujące zmianę koncentracji tlenu i siarki w czasie kontaktu stopu z parami magnezu.
EN
This paper presents a thermodynamic analysis of the reaction between [S] and [O] dissolved in liquid cast iron and magnesium in a vapour state. It has been shown that liquid cast iron treatment by magnesium increases the surface tension on a phase boundary: liquid cast iron – graphite. Excess of magnesium disolved in liquid iron may be a source of decreasing the surface tension as well. The model of magnesium, oxygen and sulphur transfer throw Nernst’s static diffusion layer in the liquid (Fe-C) alloys – Mg vapour has been presented as well. Equtions for calculation final concentration of [S] and [O] have been determined.
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